Technical Field
The present disclosure relates to the field of optical energy sources, and in particular to a diffuse reflection material, diffuse reflection layer, a wavelength conversion device and a light source system.
Description of the Related Art
At present, the excitation of a high speed color wheel by blue light laser can effectively solve the heat quenching problem with a phosphor powder to realize a high-efficiency and low-cost laser display, and has gradually developed into one of the mainstream technologies of laser light sources. In this solution, the light sources include an excitation source and a wavelength conversion device, where the wavelength conversion device includes a reflective substrate and a phosphor powder sheet coated onto the reflective substrate, as well as a motor for driving rotation of the reflective substrate, to allow light spots formed on the phosphor powder sheet by exciting light from the excitation source to act on the phosphor powder sheet according to a round path.
Mirror aluminum is employed as the reflective substrate in an existing wavelength conversion device. High purity aluminum or high purity silver is employed as the high reflection layer in such mirror aluminum. With the increase in the light source power of lasers, mirror silver/aluminum suffers from an increasingly severe problem of nigrescence due to oxidation at a high temperature. In order to solve this problem, a diffuse reflection layer formed by white diffuse reflection particles adhered by an adhesive agent, or a porous reflective ceramic is generally employed in place of the silver/aluminum plated metallic reflection layer, so as to avoid, to a certain extent, the problem of decrease in the reflective index of the reflective layer at high temperature.
However, the reflection mechanism of such diffuse reflection layer is multiple scattering-reflection generation of specific light wave by the scattering particles. In order to achieve a higher diffuse reflective index in the diffuse reflection layer, the film layer thereof must achieve a greater thickness, and generally a thickness of 200 μm or more. However, with respect to a thickness of hundreds of nanometer of the medium protection layer of a mirror silver surface, such film thickness will increase the conduction paths of heat generated by the fluorescent layer, thereby leading to a higher thermal resistance, which is adverse to luminous thermostability of the wavelength conversion device. How to take account of both luminous efficiency and thermostability of a wavelength conversion device has become a new issue for the research and development personnel.
At present, a higher reflective index can be realized at a lower thickness by employing high reflection particles submicrometer-sized aluminum oxide and adjuvant particles titanium dioxide with a strong covering power. However, wavelength conversion devices formed by this material lack in luminous stability when excited with a laser at a high power density. Therefore, there is still a need for modifications in the existing wavelength conversion devices, so as to improve the luminous efficiency and thermostability thereof.